Application manual
KNX room temperature controller EK-EQ2-TP
Release 3.00 - Updating: 27/06/2017
Application Manual
© SBS S.p.A. - All rights reserved
Page 85
This type of control is well suited for use with ON / OFF actuators, such as electrothermal actuators and
drives for zone valves, which are less expensive than proportional actuators.
A distinctive advantage of this type of control is that it eliminates the inertia of the system: it allows significant
energy savings, because unnecessary interventions on the system introduced by the 2-point control with
hysteresis are avoided and only the power required to compensate the losses of the building is supplied.
Every time the user or the supervisor changes the desired temperature setpoint, the cycle time is interrupted,
the control output is reprocessed and the PWM restarts with a new cycle: this allows the system to reach its
steady state more quickly.
System terminals
Proportional band [K]
Integral time [min]
Cycle time [min]
Radiators
5
150
15-20
Electrical heaters
4
100
15-20
Fan-coils
4
90
15-20
Underfloor radiant panels
5
240
15-20
The following are guidelines for the choice of parameters for a proportional-integral PWM control.
Cycle time: for low inertia systems, such as air heating and conditioning systems, short periods (10-15 minutes) have to be
choosed, in order to avoid temperature fluctuations.
Tight proportional band: large and continuous fluctuations of the room temperature, short settling time to the setpoint.
Wide proportional band: small fluctuations or absence of fluctuations of the room temperature, long settling time to the setpoint
Short integral time: short settling time to the setpoint, continuous fluctuations of the room temperature around the setpoint
Long integral time: long settling time to the setpoint, absence of temperature fluctuations
OFF
ON
Cycle period
T ON
T OFF
Time [min]
OFF
ON
T ON = T OFF
Time [min]
T average ON = 50%
OFF
ON
T ON = ½ T OFF
Time [min]
T average ON = 25%